Useless bank!!!

I am highly upset I have been with FNB for years as my bank and yet they can't assist me, I have spoke to so many consultants to assist me with blocking a debit order once and for all, I was told that it was stopped and will not go through again, here we are again it's the 3rd month I've just spoke to a consultant by the name of Leoma that told me that there is nothing FNB can do what the hell as my bank I expect the debit order to be blocked because it is not authoriser at all but my bank allows it and Leoma states they can't do anything because the debit order details change every month so they cannot guarantee that it won't go through, this is insane because I have been charged unpaid debit fees as I had to stop the debits myself, I refuse to pay R400 for unpaid debit fees as I've tried to stop this debit for months now without any joy, no manager gets back to me when I request for one and I get automated mails stating my query will be looked into but never does, I do not know what to do anymore but to close my account and go to another bank because FNB IS VERY USELESS!!!!